Vergence adaptation, clinically known as prism adaptation, has been considered a homeostatic function of eye movement that compensates for extraocular muscle force change due to aging, development, disease, or fatigue. However, recent experiments using healthy subjects showed that vergence adaptation can induce a different response in relation to version, vergence, or any combination of the two. Thanks to this flexible and sophisticated mechanism of neurological adaptation, the binocular system achieves fine stereoscopic vision at any given gaze position and viewing distance.

Accommodative microfluctuations are classified into the high frequency component (HFC), 1.02.3Hz, and the low frequency component, less than 0.6Hz. HFC is considered a standard indicator of visual fatigue. We investigated the relation between HFC and pupil diameter. Results showed that HFC was high when pupil diameter was small, suggesting that pupil diameter affects HFC as an accessory function of accommodation.

Purpose: Using a wide-angle view ultrasound biomicroscopy (UBM; KINSCAN), we evaluated possibility of measuring ciliary sulcus diameter (sulcus to sulcus: STS), which is considered impossible to do directly; we also analyzed correlations between STS and other ocular measurements.

Methods: Ten eyes of 9 cataract patients were measured using UBM. Linear and multiple regression analyses were used to analyze the correlations between STS and other ocular measurements (white to white: WTW; angle to angle: ATA; anterior chamber depth: ACD; corneal curvature: K value; axial length: AL).

Results: STS was measured in all eyes. In linear regression analysis, STS showed statistically significant correlations with ACD, K value and AL, but no correlation with WTW or ATA. There was no correlation between STS and any other measurement in multiple regression analysis.

Conclusions: STS was measured directly, using a new UBM. Direct measurement is preferable, since it is difficult to derive STS from other eye measurements.